Fatty acids are an important class of lipid molecules, one of the four main building-blocks for all living tissues. Our laboratory has recently identified the branched-chain fatty acid 15-methyl hexadecanoic acid, also known as C17ISO, as required for post-embryonic growth in the nematode worm C. elegans. In the absence of this molecule, which is a methlyated palmitate and probably a catabolite of leucine, worms are unable to grow after hatching, but this arrest can be suppressed by supplementation with C17ISO. C17ISO has been implicated in the coordinated sensing of nutritional and metabolic status to allow for larval growth, but the mechanism of its action is unknown. Through genetic screens we have identified several complete-suppressor strains and a partial-suppressor strain, which suggests that C17ISO may be part of a lipid-signaling or -metabolism pathway that is essential for worm development. I propose to (1) identify the genes involved with this putative signaling pathway and (2) characterize the mechanism of the already identified partial-suppressor mutant strain.